NEW YORK -- A federal health official is expected to decide within days whether to expand an aid program for anyone sickened by World Trade Center dust to cover cancer, a move that would be cheered by many former ground zero workers, but could also prove costly and come at the expense of people with ailments more conclusively linked to 9/11's toxic fallout.

An advisory committee recommended in March that the government open up the $4.3 billion program to people with cancers in 14 different broad categories, including nearly all of the most common forms of the disease.

To date, there is little hard evidence of unusual cancer rates among people exposed to the soot that fell on lower Manhattan after the attacks. But the panel, made up of occupational health specialists, toxicologists, union officials and health advocates, said there were enough carcinogens present at the site to create a plausible risk.

Adding cancer to the list of covered conditions would make hundreds, or even thousands, of residents and rescue and recovery workers eligible for government-financed medical treatments and sizeable payments for lost wages and diminished quality of life.

But it might also put a severe financial strain on the program.

If Howard accepts the panel's recommendations in their entirety, there would likely be a surge of costly claims in a system now primarily helping people with conditions that aren't life-threatening, like asthma, chronic sinus irritation, sleep apnea or acid reflux disease.

The total number of people exposed to the dust is unknown, but 60,000 people have already enrolled in 9/11 health programs for people who lived or worked within the disaster zone, which covers most of Manhattan south of Canal Street.

Congress capped funding for the program at $1.55 billion for treatment, and $2.78 billion for compensation payments.

The special master overseeing applications for compensation, Sheila Birnbaum, said that unless Congress increases those amounts, she may have to prorate payments based on the number of people who apply and the severity of their illness.

"The addition of cancers, of course, complicates the issue," she said. Compensation awards for people with cancer -- especially fatal cases -- are likely to be significantly larger than claims being submitted now for other illnesses, she said. Any prorating based on a funding shortage would mean less money for people with other types of health problems.

That prospect has alarmed some advocates for the workers like Noah Kushlefsky, an attorney with the firm Kreindler & Kreindler, who represents about 3,800 people who intend to file claims.

"The budget should have no bearing on whether these people get help," he said. "Either we believe that illnesses were caused by the toxins that were down there -- in which case, people should be cared for -- or we don't."

It is unclear whether program administrators would make any attempt to distinguish between people who got cancer because of exposure to World Trade Center ash, and others who got it through smoking, sun exposure, bad genes or some other reason. Generally, it is very difficult, if not impossible, to determine why a person got cancer.

Under the committee's recommendation, almost all of the most common types of the disease would be added, including leukemia, non-Non-Hodgkin's lymphoma, melanoma and cancers of the breast, lung, colon, kidneys, bladder and thyroid.

Combined, those illnesses strike nearly 1 million Americans each year, killing about 333,000, according to federal health statistics. The panel also recommended adding non-melanoma skin cancer, which afflicts another 2 million Americans annually.

Those statistics assure that, even if it turns out that trade center dust has little or no impact on a person's risk of getting cancer, thousands of exposed people will get some form of the disease anyway as they age.

Elizabeth Ward, the head of intramural research at the American Cancer Society, and the chairwoman of the advisory panel, said it didn't consider cost concerns, or the fairness of the compensation system, when making its recommendation.

"Many of these people were working in conditions that, in a normal workplace, people would walk out," she said of the army of men and women who cleared ground zero of a mountain of rubble while breathing in particles that blackened their spit, irritated their eyes and throats, and made every breath uncomfortable.

"I think there is a very serious concern that these exposures were unique," she said.

Howard has already reviewed the issue once before. Last year, he decided not to include cancer patients in the program, saying science had yet to show a link between trade center dust and any type of the disease.

This year, he could again defer a decision while more scientific research is conducted, or add some types of cancer to the coverage list, but exclude others. He also has the power to set up rules governing which cancer patients might be eligible, based on factors that might include the severity of their exposure to the dust.

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